Magnetic mounting for pill-type diodes



J y' 1970 w. M. SHARPLESS MAGNETIC MOUNTING FOR PILL-TYPE DIODES Filed Nov. 14, 1967 FIG.

35 MAGNETIZED lNl/E/VTOR By W M. SHARPLESS ATTORNEY United States Patent MAGNETIC MOUNTING FOR PILL-TYPE DIODES William M. Sharpless, Fair Haven, N.J., assignor to Bell Telephone Laboratories, Incorporated, Murray Hill and Berkeley Heights, N.J., a corporation of New York Filed Nov. 14, 1967, Ser. No. 682,863 Int. Cl. B25b 11/00; H011 7/60; H0lp 7/00 U.S. Cl. 333-98 4 Claims ABSTRACT OF THE DISCLOSURE A pill-type diode is disclosed suitable for magnetic mounting within a waveguide. The end layers of the cylindrical pill, constituting the diodes terminals, are made of a magnetic material and are conductively bounded. The pill is secured within the guide by com pression between two coaxial conducting rods inserted through opposite walls of the waveguide. One of the rods is magnetized so that the pill is held magnetically during the mounting process.

BACKGROUND OF THE INVENTION This invention relates to electromagnetic wave devices and, more specifically, to devices for mounting miniaturized diodes within waveguides.

Many characteristics of asymmetrically conducting devices such as crystal diodes have made their use desirable in the high frequency range of the electromagnetic wave spectrum. In US. Pats. 2,436,830 and 2,438,521 granted to applicant on Mar. 2, 1948 and Mar 30, 1948, respectively, there are disclosed various techniques for utilizing such devices. Particularly useful are diodes mounted in pistontuned sections of a waveguide where they function, for example, as oscillators or detectors.

In the centimeter wave or longer microwave region a diode encased in a coaxial cartridge and located in the path of the propagating Wave energy is generally satisfactory. Conventionally, the diode is encased in a cylindrical ceramic package approximately A inch or more in length with end caps serving as the diodes electric terminals. For low frequency mounting, two spring contacts are soldered on the ends of wires and the diode is inserted between the spring contacts, each of which grips an end cap circumferentially. At the higher frequencies, where coaxial line and waveguide mounts are required, structural and electrical contact is usually made with pairs of jaw-spring fingers or mechanical chucks which grip the end caps of the cylindrical cartridge circumferentially. Using this mechanism, a diode can be inserted into a waveguide attached to one of these jaw-spring structures, and the mating required to complete the mount is accomplished within the guide. Removal is effected in a reverse manner.

At the higher frequencies, miniature pill-type diodes are more desirable than larger cartridge diodes since they exhibit greatly reduced inductance and capacitance. The need, therefore, arises to mount these miniature diodes Within miniature sized waveguides. Pill-type diodes are cylindrical in shape but their axial length is small com pared with the diameter of across section. A diode of this type might have an axial length of 0.025 inch and a diameter of 0.070 inch which is approximately the size of the head of a common household pin. In order to mount this tiny diode according to conventional technology, it would require machining a pair of chucks in many cases larger than the diode itself, adding undesirable inductance and capacity, and each capable of circumferentially gripping the small pill while avoiding electrical contact between themselves. This mounting technique would also required providing the pill diode with two electrically conductive end caps which extend axially on the pills cylindrical surface far enough to be gripped solidly by the chucks, while each end cap remains electrically distinct.

An alternative means of mounting small diodes within a waveguide structure is desirable in order to avoid these undesirable mechanical and high frequency electrical features.

SUMMARY OF THE INVENTION In accordance with the present invention, a pill-type diode is constructed which can be mounted within a conductively bounded waveguide using a magnetic holder. The use of a magnetic mount eliminates the diflicult problems involved in adapting conventional mounting techniques to a pill diode the size of a pin head. At least one end surface of the cylindrical pill is made of a mag netic material. As used herein a magnetic material is one such as a ferromagnetic substance which is attracted by a magnetic field such as is produced by a conventional magnet or magnetized material, and a magnetized material is one which has the properties of a magnet and sets up a magnetic field which attracts magnetic materials.

In addition to its magnetic properties, the end surface must afford good external electrical contact since the end surfaces of the pill constitute the terminals of the diode. This combination of properties is provided by using as an end layer of the cylindrical pill an iron alloy having good electrical conductivity and bonding a high conductivity material to its outer surface. The pill is a cylindrical sandwich having a conductively bounded iron alloy bottom end layer, a semiconductor diode bonded to the bottom end layer, and a conductively bounded top end layer. For the embodiment selected, the top and bottom ends are both made of the same magnetic material.

The pill diode constructed in accordance with the present invention has an outer casing which provides good electrical conductivity and a magnetic surface, thus permitting the pill to be supported by a magnetized holder. The mounting device magnetically provides structural connection between one end of the pill and a surface of a removable member of the mount. The pill may therefore be positioned within or removed from any inaccessible location into which the removable member may be inserted.

Magnetic attraction between the diode and the removable mounting member causes the pill to remain fixed in place on the surface of this member during the mounting process. The removable member with the pill afiixed is inserted into the desired location which may be, for example, a waveguide section. A second member of the mounting mechanism, inserted from the opposite direction, provides pressure to the second end of the pill by means of a spring, causing the pill to be firmly compressed between the two members of the mount.

Electrical connections to the diode are made simultaneously with the structural support. The opposing ends of the pill constitute the two diode terminals and the mounting members act as conductors. For effective electrical contact, the mating surfaces of the rods should be plated with a low resistance material such as gold.

It is one object of the present invention to provide a pill-type diode which can be mounted in an inaccessible location. It is further desirable to provide a device which facilitates easy mounting and removal of a pill-type electronic component, such as a diode, within a waveguide section.

These objects are accomplished by packaging a diode so that it can be magnetically attached to a movable structure. Thus supported, the diode is placed in a desired position where it is firmly fixed by compression. In addition to mounting diodes, magnetic mounting can, of course,

be employed to hold other types of miniature electronic components.

BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other objects and features of the invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings in which like numbers are used to designate identical elements throughout.

In the drawing:

FIG. 1 is a cross-sectional view of a pill-type diode suitable for mounting in a magnetic holder;

FIG. 2 is a plan view particularly in cross section of a piston-tuned waveguide section in which a pill-type diode is mounted in accordance with the present invention; and

FIG. 3 is an exploded view of the pill-type diode and the adjacent members of the mounting structure.

DETAILED DESCRIPTION Referring to FIG. 1, there is shown, by way of example a diode suitable for mounting in a waveguide using a magnetic holder. The design of this diode is such that the lead inductance and barrier capacity have been reduced to a minimum while maintaining the high efficiency characteristics of a Schottky barrier rectifier. This diode is expected to show low conversion loss and noise ratios at frequencies well above X band.

The complete diode package 11 is about 0.070 inch in diameter and approximately 0.025 inch high. The semiconductor material is N-type epitaxial gallium-arsenide of the polka-dot type composed of substrate 12 and epitaxial layer 13.

Substrate 12 is soldered or otherwise affixed to lower disc 14 as shown. Disc 14 is made of Kovar, an iron alloy containing nickel, cobalt, and maganese. As is well known in the art, Kovar is a magnetic material and a good electrical conductor, and its thermal expansion is covariant with glass. Thus Kovar is an excellent material for casings of small semiconductor devices especially where glass or quartz are used as insulators.

Point 16 is electrolytically pointed 0.0005 inch round phospho-bronze wire which is gold-plated. This point makes a firm low resistance contact to one of the numerous four micron diameter gold dots 17 previously disposed on the 0.5 micron thick epitaxial surface 13. After the desired contact is made, the point is locked in place with a layer of low loss epoxy cement 18. The finished ruggedized diode, bonded to disc 14, is about 0.012 inch high. A second Kovar disc is mounted as shown insulated by quartz spacer 19. Point 16 extends through off center hole 20 in disc 15 and is affixed to the exterior of disc 15 by solder 21. Discs 14 and 15 are the diode terminal and their exterior surfaces are plated with thin films of gold 22 which prevents corrosion of the Kovar surface and provides low resistance low loss contacts.

Referring to FIGS. 2 and 3, there is shown by Way of example, a diode mounting assembly within a pistontuned conductively bounded Waveguide section 31. As described above, the end surfaces 32 and 33 of diode package 11 are made of a magnetic material. The pill will be held in place when end 33 of package 11 is positioned on corresponding end 34 of magnetized rod 35. Rod 35 has a diameter slightly larger than the diameter of diod package 11 and is mounted tightly in an axial hole in the center of matching probe 36. Rod 35 is affixed to probe 36 depressed slightly from surface 37 of probe 36. Diode package 11 is placed in the depression so that end 33 of package 11 is in contact with end 34 of magnetized rod 35. By means of external threading 43, matching probe 36 is inserted through lower broad waveguide wall 38 with package 11 attached. Pressure is applied to opposite end 32 of diode package 11 by small metal Eontact spring 40 located on the end of a second cylindrical rod 41. Rod-.41 and spring 40 are not magnetized. Rod 41 passes through cylindrical hole 47 in the wall of output trap 48 which is mounted in upper broad waveguide wall 39. Rod 41 is insulated electrically from output trap 48 by a layer of insulation 49, such as Teflon, which is attached to the cylindrical wall of hole 47. Axial movement of rod 41 is prevented by set screw 50, made of insulating material such as nylon, positioned as shown.

As was described above, ends 32 and 33 of diode package 11 constitute the electrical terminals of the diode are plated with a layer of high conductivity material. For good electrical contact, spring 40 and end 34 of rod 35 should likewise be plated with a high conductivity material. Gold is a suitable material for this purpose, and will provide gold contact at both terminal connections. Electrical connection of the diode to an external circuit is provided through rod 41 and through the waveguide walls via probe 36. The conduction path from the diode package 11 to waveguide wall 38 is improved by gold plating surface 37 of probe 36 as well as end 34 of rod 35.

Waveguide section 31 may be tuned by adjustment of piston 51 as is well known in the art. Impedance matching can be achieved by experimentally advancing and retracting probe 36 by means of threading 43 and correspondingly threaded locking nut 44. Advancing and retracting trap 48 by means of threading 45 and correspondingly threaded locking nut 46 will further improve matching. A very broad-band, low standing wave ratio match to the diode is accomplished by adjusting the position of both trap 48 and probe 36, together with piston 51.

One advantage of the diode configuration described above is that the diode package is structurally symmetrical. Since each end is made of Kovar, both ends have magnetic properties. Therefore, the polarity may be reversed when desired and the pill may be mounted with either end in contact with the magnetized rod when used as an unbalanced single diode detector. For use as a balanced detector, the structural symmetry is especially desirable as either of the pill diodes may be reversed with respect to the other without altering the mounting structure. Thus the need for providing means of electrically reversing the direction of current flow by using one P and one N type diode or by employing complicated external circuitry to do the compensating is eliminated.

While the invention is shown with diode package 11 electrically connected to Waveguide wall 38, it is to be clearly understood that diode package 11 could be isolated from the waveguide wall and the necessary external connections provided by additional circuitry. Further, if it is desired to electrically DC isolate diode package 11 from rod 35, probe 36, and waveguide wall 38, a thin layer of dielectric material such as mica may be substituted for gold layer 37. Without affecting the magnetic attraction the dielectric material would allow only a high frequency capacitive coupling to waveguide wall 38 without providing a DC current path.

Although the invention has been described as a diode mounting for a piston tuned waveguide section, it is to be clearly understood that this mounting device is adaptable to any structure in which a pill-type electronic component, diode or otherwise, is internally mounted. A transistor, for example, could be mounted with a first terminal connected to probe 36 and the other two terminals connected individually to two discrete conductive paths associated with rod 41.

In all cases it is to be understood that the above-described arrangements are merely illustrative of a small number of the many possible applications of the principles of the invention. Numerous and varied other arrangements in accordance with these principles may readily be devised by those skilled in the art wihtout departing from the spirit and scope of the invention.

What is claimed is:

1. Apparatus for mounting an electronic component comprising in combination:

a cylindrical package containing said component including a plurality of terminals of said component on the exterior of said package, at least one end surface of said package being of a magnetic material;

a magnetized structural member for magnetically attracting said one magnetic end surface of said package;

a nonmagnetized structural member mounted coaxially with said magnetized member for compressing said package axially between said magnetized and nonmagnetized members providing structural support of said package;

means for making electrical contact between said plurality of terminals and an external circuit through at least one of said members.

2. In combination, a conductively bounded waveguide;

a semiconductor diode;

a cylindrical package in which said diode is held including two conductively bounded ends of said package connected as electrical terminals of said diode, at least one of said ends being of a magnetic material;

a magnetized rod magnetically attracting said one magnetic end of said package and having means for making electrical connection with said one magnetic terminal end of said package, said magnetized rod being inserted through and secured to a wall of said waveguide and said diode being magnetically attached axially thereto;

a nonmagnetized rod inserted coaxially with said magnetized rod through and secured to an opposite wall of said Waveguide; and

means for maintaining rigid contact between said nonmagnetized rod and said package, and for making electrical contact with a second terminal end of said package.

3. A combination as claimed in claim 2 wherein said magnetized rod is of slightly larger diameter than said package and said magnetized rod is mounted within a probe with its end depressed slightly from the surface of said probe so that said package fits into the depression when magnetically attracted to said magnetized rod, and wherein said means for maintaining rigid contact and for making electrical contact is a conductive spring located on the end of said nonmagnetized rod so that said spring is pressed against said second terminal end of said package when said nonmagnetized rod is inserted through and secured to said opposite wall.

4. In a waveguide,

a first mechanical element capable of conducting electrical signals;

a pill sized electronic component Within a package;

means for magnetically holding said package to an extremity of said first element, said first element being inserted through a wall of said waveguide and secured thereto such that said extremity projects into said waveguide;

a second mechanical element capable of conducting electrical signals, said second element being inserted through a wall of said waveguide and secured thereto such that said second element and said first element provide axial structural support of said package and make electrical contact through said component.

References Cited UNITED STATES PATENTS 3,142,783 7/1964 Warren 317-101 2,991,347 7/ 1961 Weinstein 269-8 X 3,038,139 6/1962 Bonanno. 3,178,796 4/ 1965 Smits. 3,223,903 12/1965 Solomon 317-236 X 3,254,279 5/1966 Cohn et a1 317-236 3,316,494 4/1967 Harrison et al 329-161 3,360,851 1/1968 Kahng et al. 2,472,938 6/ 1949 Brittain et al.

OTHER REFERENCES Magnetic Jigs Simplify Diode Measurements, pp. 44- 4,5, Electrical Design News, December 1963.

ALFRED L. BRODY, Primary Examiner US. Cl. X.R. 

